A panel investigating the causes of Japan's 2011 Fukushima nuclear disaster is hearing testimony from several key national figures.

Among those giving evidence are then-Prime Minister Naoto Kan and Masataka Shimizu, the former president of Tokyo Electric Power Co (Tepco), owner and operator of the Fukushima Dai-ichi Nuclear Power Plant, where multiple meltdowns occurred following the March earthquake and resulting tsunami. Kan, who was since replaced by Yoshihiko Noda, said that he had gone to Fukushima directly after the earthquake, seeking to keep Tepco workers from leaving the reactors. Shimizu has yet to testify but is expected to have to defend his three-day absence right after the tsunami, when he had to be hospitalized for high blood pressure and dizziness.

Anger with the meltdown gripped many in Japan, and Kan and Shimizu were both targets of that anger. Tepco recently released revised radiation figures, showing that the amount released after the meltdowns was more than two times that estimated at the time. Tens of thousands of people had to find temporary homes, some for many months, and the total cost of the disaster has recently been re-assessed at $100 billion.

The distrust of nuclear power remains high in the country, which usually depends on nuclear reactors for a large part of its power supply. A 2010 plan had called for increasing nuclear sources to a full 50 percent of the country's power supply, and the government was moving toward implementing the plan when the twin disasters struck.

One by one, the country's nuclear reactors have been shut down, some for good and others awaiting orders to restart. In the wake of the shutdowns, many power companies have continued with non-standard schedules of power supply and employment. As the weather gets hotter, the country's power supply will come under increasing strain.